Submarine signaling



R. D. FAY.

SUBMARINE SIGNALING.

APPLICATION FILED MAR- 26, I920.

1,380,-869. Patented June 7, 1921.

2 SHEETS-SHEET 1.

/7- TDENE ys R. D. FAY.

SUB MARINE SIGNALING. APPLICATION FILED MAR. 26. 1920.

1,380,869. Patented June. 7, 192 1.

2 SHEETS-SHEET 2- feet.

ilNiTE-ZD STATES PATENT @FFNE.

s enna) n. FAY, or nnnaiv'r, nassacnusnrrs, assreuon r0 HAMMOND v. QA ornosron, MASSACHUSETTS.

sunnmnmn SIGNALING.

Specification of Letters Patent.

lPatented June 7, 1921.

Application filed March 26, 1920. Serial No. 369,064.

To all whom it may concern Be it known that I, RICHARD D. FAY, ofNahant,'in the county of Essex and State of Massachusetts, a citizen Ofthe United States, have invented a new and useful Improvement inSubmarine Signaling, of which the following is a specification.

In most devices" heretofore employed for sending and receiving sounds inwater or in air, diaphragms have been used having one surface in contactwith the water or air, and it has been the motion of the center of suchdiaph ragms that hasbeen the most active agency in producing the desiredef- Diaphragms with fixed edges such as have heretofore been employedhave certain inherent characteristics of which the two following needonly be cited (a) diaphragms with clamped edges have proved veryeflicient both in sending and in receiving, but have their limitationsowing to the natural frequency of the diaphragm itself and particularlyto the nodal vibra tions which are usually present and are often of anenergy sufficie-nt to interfere seriously with the propagation of thewaves of a useful frequency; and (b) moreover, it is im-' portantthat-the amplitude of motionof a. diaphragm or the like in thepropagation of waves in water should not exceed a certain well definedlimit, for, if this limit is passed, cavities are produced in the waterwhich seriously reduce the amplitudes of the propagated waves.

A good transmitter or receiver of sounds must be so arranged;

(a) That practically all of the energy is used in transmitting sounds ofthe desired or necessary frequency; (1)) That in an under water devicethe motion at the surface of discontinuity, i. 0., between thewater andthe sound-producing or receiving device, shall never exceed a definiteextremely small amplitude (c) That at all points on the surface ofdiscontinuity the movements will be as nearly as possible of likeamplitude and phase; and,

(d) That the arrangement shall be such that the device will be equallyeffective as a producer or receiver of compressional waves.

I have accomplished the above-described results by the use of anarrangement in which an elastic rod of proper length and diameter isemployed. This rod is made to act upon a plate having a substantiallyplane surface whlch surface is in contactwith the water or'airand is sodesigned mechanically that will not be distorted by the pressuresexerted upon it when the device is used either for sending or receivingcompressional waves such as those of sound.

By the use of my invention I ain able to obtain results which so far asI know have never before been obtained and are, I am satisfied,essential to the best construction of underwater sound-sending andreceiving devices, for when sending, I am enabled to utilize a source ofvibrations requiring relatively large amplitudes for its efficientoperation, reducing such vibrations,'substantially without loss ofenergy, at the surface of discontinuity between the sound-sending.

device and the water; and, when receiving,

brations are transformed into similar waves of electricity. Moreover,this may be accomplished by my invention in such a way as to insure to aremarkable degree the transmission of only the waves of the desired andnecessary frequency.

In the practical construction of my de-' vice as a producer of soundwaves in water, any convenient form of vibrator can be used. Inembodying my invention I utilized a Fessenden oscillator (see U. S.Patent No. 1,167,366) vs'o modified that the diaphragm of the oscillatorserved primarily as a means of supporting one end of the rod. The otherend of the rod was expanded, for a small distance, into the form of ahollow cone in such a manner that the cross-sectionalarea of the metalportion of the cone was at all points equal to the cross-sectional areaof the rod. The conical form given to the end of the rod is for thepurpose of distributing the contact between the rod and the plane orsubstantially plane surface which is in contact with the water, and byso doing to assist mechanically in keeping that surface undistorted bythe changing pressures exerted upon it. Any system which will distributethis contact will serve equally well provided the area of its crosssection be kept constant.

In the Fessenden oscillator and in practically all sending and receivingdevices there is a considerable amplitude of motion. On the other hand,the motion of the surface in contact with the water must be relativelysmall. It is this ratio of amplitudes at the two ends of the rod whichis one of the important factors to be considered in the design of themechanism.

To take the simplest form of my invention where the rod is of equalcross area throughout its length .and one end is attached rigidly to aplate which-isin contact with water or other medium and is of suchrigidity as not to be distorted and with the resistance exerted whenthis plate is vibrated under working conditions, there are wavesreflected fromthe plate back along the rod and each reflected wave willmeet the advancing wave at some point along the rod. The rod should beof such length that the time required for the advancing wave I as asender.

to travel through it to this point shall be one quarter of the period ofvibration of the transmitted wave. This is the shortest length of rod.If rods of longer lengths are to be used, the distance from thevibrating mechanism to the point of meeting of the pressure waves mustbe 357, etc., quarter wave lengths. In other words, the main feature inthis portion of the invention is the use of an elastic rod to connectthe point of maximum vibration with that of minimum vibration of alength from the point of maximum vibration to the point of meeting ofthe direct and reflected pressure Waves equal to an odd number ofquarter wave lengths of sound of the desired frequency in the rod. Ifthis principle is recognized it is notnecessary to employ a rod ofuniform cross section throughout its length, although thecross-sectional area of the metal in the cone and of that portion of therod which extends from the cone to the point of meeting should besubstantially equal. It is necessary only todesign the rod so that thetimes of propagation of the direct and reflected waves are such as willproduce a point of meeting of such waves at odd multiples of the quarterwave length from the end having maximum motion.

The cross-sectional area of the rod between the plate and point ofmeeting of the waves controls the ratio of the amplitude at the two endsof the rod. For ease inexplanation the device will be considered at thepoint of meeting of pressure waves and at the generator is due to thelength of rod between these points being such that the amplitudes of thegenerated and reflected waves will assist at the generator end. andoppose at the point of meeting of pressures of the waves generated andreflected. Evidently the greater the amplitude of the refleoted waverelative to that of the gener- The difference of amplitudes found thatwhen waves of a frequency of ated wave, the greater will be the ratio ofthe amplitudes at these two points. Hence, by giving the rod suitablecross section the amplitude of the reflected wave can be controlled andhence the amplitude ratio at these two points can be given any desiredvalue. Clearly, with a 'rod of given size, the larger the area of theplate in contact with the water, or other liquid or gaseous medium, andthe greater the weight of the plate acting on such medium, the greaterwill be the reflection. While in most cases it will be desired to havethe reflected wave in phase with the generating wave at the end havingmaximum amplitude, it is possible to vary the phase of the reflectedwave so that it will in effect add to or subtract from the weight of themoving parts of the vibrating device and hence change the frequency ofthe vibrations at which best efliciency is obtained. Such an arrangementis the simplest form in which the fundamental principle is utilized. Itis clear, however, that a weight fastened to any part of the rod willcause additional reflections and I have found that the effect of theweight is equivalent to using a rod of different'section or differentlength or both according to the magnitude of the weight and its positionon the rod. Hence a weight or weights whose position on the rod may bevaried furnishes a convenient means either forvarying the frequency atwhich the desired ratio of amplitudes at the ends of the rod is obtainedor for varying the ratio of amplitude at any frequency. In particular bythe use of a weight a shorter rod may be made to give a'desiredamplitude ratio than would be possible if the weight were not used.

Furthermore,'it'is not necessary that the rod should have its fulllength between the yibrator, or microphone, and the plate. It ispossible to obtain the same effect by using a rod inside of a pipehaving the same area of cross section as the rod and having one end ofthe rod attached to one end of the pipe. In this case the free end ofthe pipe takes the place of the cone and is attached to the plate, themicrophone or vi- .brator is fastened to the free end of the rod insideof the pipe and the combined rod and pipe are equivalent to a continuousrod of the same section and of their combined lengths.-

Following out the above principles, I have tive. In the device which Ihave used the rod is expanded at its conical end to a di ameter ofinches in a length of inches,-

. ticular device a rod of uniform cross-sectional area between the endof maximum movement and the plate in contactwith the water is used.

In the drawings Figure 1 is a side elevation partly in section of adevice embodying the invention.

Fig. 2 is a similar view showing a different mounting of the contactplate, which is capable of being used in the air.

Fig. 3 is a side elevation of the device with microphone attachedthereto.

Fig. 4 is a side elevation of a device embodying my invention withweight on the rod.

Fig. 5 is a similar View partly in section showing another way ofmounting my devlce,

Fig. 6 being a section on line 6-6 of Fig. 5.

Fig. 7 is a view partly in section of a modification of my invention.

In Fig. 1 A is the mechanism used in transforming electricaloscillations into mechan-1 ical vibrations or transforming mechanicalvibrations into electrical oscillations such as'a Fessenden oscillator.Bis a rod preferably made of steel so'as to be elastic. One end of thisrod is connected to the diaphragm of the oscillating device and formismade by the use of a hollow cone D which preferably is integral with therod B and the cross-sectional area of the metal of which is equal tothat of the rod. The thickness of plate C and the large'diameter of theend of .the cone D attached to it insure that all points in the surfacein contact with the water, will when vibrated, move backward and forwardwith equal amplitude. WVhen alternating currents of a definite frequencyare passed through the oscillator, waves of compression are propagatedalong the rod and are partly reflected at the other end of the rod. Therod is given such length that the reflected wave will reach theoscillator in phase with its motion and thus tend to assist inincreasing the amplitude of its movements. The more these waves arereflected the smaller Will be the amplitude of motion at th water end ofthe rod and the greater will be the amplitude of motion at theoscillator end. When used as a receiving device the action will be thesame. A

having maximum motion.

ment the button is agitated more violently very small motion at thewater end of the rod will operate to produce a larger amplitudeof motionat the oscillator end of the rod and, consequently, induce greatcurrents in the oscillator used as a generator of electrical currents.

In Fig. 2 a similar arrangement is shown, except that in this case theplate C to which the rod B is attached by the cone D is in an opening ina partition or frame F which has a flange or packing G passing aroundthe edges to the back of the piston. This form of the invention may beused for other signals than those sent from shipboard.

In Fig. 3 the same device is shown having a microphone button H attachedto the end By this arrangeby a sound Wave coming through the water thanwould be the case if the button were attached to the skin of the ship.

When a rod is used with a microphone, noises and vibrations which arecarried by the skin of the ship may be reduced by having the plate formthe back of a tank G of which the skin of the ship or other part E formsthe front (see Figs. 5 and 6). The plateis insulated acoustically fromthe sides of the tank with rubber or similar material L. The tank whichneed not be completely inclosed is filled with water-G In. this case theplate may conveniently be made in two sections C C which are clampedtogether by screws, the rubber insulating member being in the form ofadisk and clamped between them. The edge of the part L is clampedagainst the end of the tank G by a ring 7'.

In Fig. 7 instead of a rod as shown in the other figures an equivalenttherefor is shown, the cover D terminating in a tube D to which isattached at its outer end by a plate 6 or other form of attachment a rodB which lies within the tube and carries a microphone at its inner end.The combined length of the tube and the rod should be governed by thesame rule as in the other forms of my invention.

While the rod and its cone is shown and described as being made in onepiece, the invention is not limited to that construction,

the invention relating rather to the provision of a continuousuninterrupted path of the general character described for vibrationsfrom a vibrator to a substantially rigid plate such that the plate willbe vibrated bodily by the vibrations conducted by the elastic rod andaugmented because of the elasticity of the rod, and'for this purpose therod need not be integral nor need the cone engage the plate around itsentire edge so long as the area of the cross section of the parts of thecone which engage the plate is substantially equal to the cross sectionof the rod adjacent to it as above described and that these parts inengagement with the plate, shall so contact with the plate as to cause.it to vibrate as a whole without distortionf In using the term rod Imean to include both a solid rod and a hollowrod or tube either ofwhich, if properly proportioned as to length and metallic cross, area,will provide such a continuous uninterrupted track for longitudinalvibrations as is required to secure the desired result.

\Vhat I claim as my invention is 1. A device of the kind describedcomprising two members and a rod connecting said members, said rod beingmade of elastic material whereby the motion of one of said members, whentransmitted longitudinally.

through said rod to the other member, will have its amplitude changed."

2. A device of the kind described comprising twomembers, one memberhaving a large freedom of movement and the other having a relativelysmall freedom of movement, and a rod connecting said members, said rodbeing made of elastic material whereby the motion of one of saidmembers, when transmitted longitudinally through said rod to the othermember, will have its amplitude changed.

3. A device of the kind described comprising two members and a rod ofsubstantially uniform cross-sectional area connected rigidly to both ofsaid members, said rod being made of elastic material whereby the motionof one of said members, when transmitted longitudinally through said rodto the other member, will have its amplitude changed.

4. A device of the kind described comprising two members, one memberhaving a large freedom of movement and the other having a relativelysmall freedom of movement, and a rod connected rigidly'to both of saidmembers, said rod being made of elastic material whereby the motion-ofone of said members, when transmltted through said rod, will set upmovements of different I amplitude in the other member, the end of saidrod attached to the member having small freedom of movement beingexpanded, without change in cross area, whereby the rod will engage themember having small freedom of motion near its outer edge and the forcesexerted at their points of engagement will include a large area.

5. A device of the kind described comprising two members, one having alarge freedom of movement and the other having a relatively smallfreedom of movement, and an elastic rod connecting said members andadapted to transmit vibrations longitudi nally from one member to theother, the length of said rod being such that at a point thereonapproximating one quarter wave length from one member the Wave reflectedfrom the other member will meet a wave originating at the first memberin opposite phase thereto.

6. A device of the kind described comprising a member having largefreedom of movement, a member having small freedom of movement and anelastic rod connecting said members, the member havingsmall RICHARD ,1).FAY.

